The present disclosure relates generally to shoulder prostheses, and more particularly to shoulder prostheses configured for use in shoulders having glenoid vault erosion or defects.
A typical shoulder or glenohumeral joint is formed in a human body where the humerus 10 movably contacts the scapula 12 as shown in FIG. 1. The scapula 12 includes a glenoid fossa 14 that forms a socket against which the head of the humerus 10 articulates. At this socket, the scapula 12 includes cartilage 16 that facilitates such articulation. Beneath the cartilage is subchondral bone 18 that forms a wall of a glenoid vault 20 that defines a cavity which contains cancellous bone 22. The subchondral bone 18 that forms the glenoid vault 20 defines a glenoid rim 21 at a periphery of the glenoid vault that is attached to the cartilage 16 (see FIG. 1). During the lifetime of a patient, the glenoid fossa 14 may become worn, especially at its posterior and/or superior portions thereby causing severe shoulder pain and limiting the range of motion of the patient's shoulder joint. To alleviate such pain and increase the patient's range of motion, a shoulder arthroplasty may be performed.
Shoulder arthroplasty often involves surgical replacement of the glenoid fossa with a conventional glenoid prosthesis such as the one disclosed in U.S. Pat. No. 6,911,047, the disclosure of which is herein incorporated by reference. The glenoid prosthesis, when implanted, provides a new laterally-facing bearing surface, which may be concave or convex, for articulation with a complementary bearing surface of a natural or prosthetic humeral head. Such conventional glenoid prosthesis is typically formed from UHMW polyethylene, titanium, or cobalt chrome and includes bone anchor(s) such as peg(s), screw(s), post(s), or a keel extending from a back side of the device opposite its bearing surface. So configured, the back side of the prosthesis is typically secured against subchondral bone of the glenoid vault while the bone anchor(s) may extend into the cavity of the glenoid vault whereby it may become anchored to cancellous bone located within the glenoid vault.
However, there are situations in which the subchondral bone support surface (including the glenoid rim) and underlying cancellous bone located within the glenoid vault may have become significantly deteriorated such that support and anchoring of a conventional glenoid prosthesis may be difficult. One such situation occurs when a patient experiences chronic subluxation of the shoulder that causes posterior erosion of the glenoid in which subchondral and cancellous bone of the glenoid is slowly worn away over time. Another such situation is seen when a conventional glenoid prosthesis is removed during a revision shoulder surgery. The removal of the conventional glenoid prosthesis reveals glenoid defects that were caused by repeated shoulder movement after the conventional shoulder prosthesis had become inadvertently loosened. Thus, in situations where there exists a significant amount of deterioration of the subchondral and cancellous bone, implantation of a conventional glenoid prosthesis described above may not be appropriate due to a lack of proper bone stock.
What is needed therefore is an improved prosthesis assembly for use in patients having deterioration of their subchondral support surface (including the glenoid rim) and underlying cancellous bone of their glenoid vault.